Cleanroom reverse-engineering is neither illegal nor immoral.
Says someone who has obviously never spent a few million on employing numerous people (plus office space etc.) to develop and maintain the intellectual property required if you want to be successful in the software industry.
If you are a software only company such as Adobe, then the intellectual property in your software is your only real asset. Hence it is justifiable to be more than slightly annoyed if some spotty oik comes along and reverse-engineers it when the license you grant with your software does not permit it.
We're talking about taking a file format & working out how to read & display it.
Describe it how you like. That's still reverse-engineering.
From the Adobe Flash Player license agreement (my bold) :
4.5 No Modification or Reverse Engineering. You shall not modify, adapt, translate, or create derivative works based upon the Software. You shall not reverse engineer, decompile, disassemble, or otherwise attempt to discover the source code of the Software. If you are located in the European Union, please refer to the additional terms at the end of this agreement under the header “European Union Provisions,” in Section 16.
16. European Union Provisions.
Nothing included in this agreement (including Section 4.5) shall limit any non-waivable right to decompile the Software that you may enjoy under mandatory law. For example, if you are located in the European Union (EU), you may have the right upon certain conditions specified in the applicable law to decompile the Software if it is necessary to do so in order to achieve interoperability of the Software with another software program, and you have first asked Adobe in writing to provide the information necessary to achieve such interoperability and Adobe has not made such information available. In addition, such decompilation may only be done by you or someone else entitled to use a copy of the Software on your behalf. Adobe has the right to impose reasonable conditions before providing such information. Any information supplied by Adobe or obtained by you, as permitted hereunder, may only be used by you for the purpose described herein and may not be disclosed to any third party or used to create any software which is substantially similar to the expression of the Software or used for any other act which infringes Adobe or its licensors’ copyright.
As you can see, even in the EU, which takes a more generous stance, you may only reverse-engineer in order to achieve interoperability with the Adobe software (e.g. to enable the Adobe software to work with your Operating System). It still does not permit you to reverse-engineer to create a competing product.