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Terms of Service

// LEGAL PROTOCOL · APPLICATION & SERVICE TERMS · EFFECTIVE SEPTEMBER 14, 2026

Welcome to StackCalc. These Terms of Service ("Terms") govern your access to and use of the StackCalc32 application on iOS, iPadOS, and watchOS, the https://www.stackcalc.io website, and associated physical hardware documentation and assembly kits (collectively, the "Services").

By downloading, installing, accessing, or purchasing products through StackCalc, you agree to be bound by these Terms. If you do not agree to these Terms, please do not use the application or website.

1. License & Permitted Use

1.1 Mobile & Wearable Software

StackCalc grants you a personal, non-exclusive, non-transferable, revocable license to use the StackCalc32 software on Apple-branded devices (iPhone, iPad, Apple Watch) in accordance with the standard Apple Media Services Terms and Conditions and Licensed Application End User License Agreement (Standard EULA).

1.2 Open Hardware & Firmware

StackCalc publishes selected printable and teaching materials for the current prototype, including the four-part mechanical STL set and Learning Lab teacher PDFs. Electronics source, firmware source, CAD generators, manufacturing artwork, and production documentation are not part of the public release. Availability of a printable file does not represent a completed powered calculator or a manufacturing qualification.

2. Computational Accuracy & Disclaimer of Warranties

StackCalc32 is engineered with meticulous care to implement authentic Reverse Polish Notation (RPN), arbitrary-precision rational arithmetic (exact fractions), numerical root finding, and scientific algorithms.

However, all calculations, formulas, numerical integration results, and graphs are provided strictly "AS IS" and "AS AVAILABLE":

  • No Safety-Critical Guarantee: While our cross-surface fuzzing harness and unit test suite verify millions of operations, StackCalc is not certified for life-critical, medical, aerospace, or hazardous industrial control applications.
  • User Verification: You acknowledge and agree that you are solely responsible for independently checking and verifying all calculations, units, and mathematical outputs before relying on them for structural engineering, critical business decisions, or academic submissions.
  • No Warranties: To the maximum extent permitted by applicable law, StackCalc disclaims all warranties of any kind, whether express, implied, statutory, or otherwise, including but not limited to the implied warranties of merchantability, fitness for a particular purpose, and non-infringement.

3. Educational & Academic Integrity

StackCalc is built to empower students with deep spatial intuition and conceptual understanding:

  • Classroom & Exam Use: StackCalc includes an Exam Mode configuration (accessible via FLAGS) that locks dynamic programmability to conform with standardized testing requirements. Users and proctors are responsible for ensuring compliance with specific institutional examination rules.
  • Authentic Learning: Our fraction manipulatives, step-by-step equation solver, and interactive TUI plots are designed to assist comprehension, not circumvent original thinking.

4. Physical prototypes and future products

StackCalc currently publishes selected printable prototype files and teaching materials. The pictured calculator is an unpowered mechanical prototype; its RP2350 board design is in fabrication. StackCalc does not offer a physical calculator for direct purchase through stackcalc.io at this time.

If a physical product becomes available through a named marketplace, the listing will identify the offered revision, contents, processing time, warranty, and return policy. The marketplace listing and applicable law govern that purchase.

5. Intellectual Property

The name StackCalc, the 4-Level Stack debossed emblem, user interface themes (RetroFuturism, Stealth Industrial, Supernova, Deep Space, Voyager), website content, and original graphics are the property of StackCalc Engineering.

  • Apple, iPhone, iPad, Apple Watch, and watchOS are trademarks of Apple Inc., registered in the U.S. and other countries.
  • HP-32SII, HP-42S, and HP-15C are referenced solely for historical context, backwards compatibility, and mathematical pedigree comparison.

6. Limitation of Liability

To the fullest extent permitted by applicable law, in no event shall StackCalc, its founders, contributors, or suppliers be liable for any indirect, incidental, special, consequential, or punitive damages (including loss of data, loss of profits, calculation errors, or academic or business interruptions) arising out of or in connection with your use or inability to use the software, hardware, or website.

7. Governing Law

These Terms shall be governed by and construed in accordance with the laws of the State of California, United States, without regard to its conflict of law principles.

8. Modifications to Terms

We reserve the right to revise these Terms at any time. Any changes will be published directly to this page (https://www.stackcalc.io/terms/) with an updated effective date. Continued use of the Services following posted changes signifies your acceptance of the updated Terms.

9. Contact Us

If you have questions regarding these Terms of Service: