well i only know that adobe sells photoshop CS2 for free.

Yeah, and /technically/, they put up a notice that you may only use the free keys if you actually own a license for that version.

No there is not, and CS2 may be free but they no longer have support for that version. Only reason they offer it for free also is because they shut down the 10+ year old servers that supported the software and handled the verification of the software when you installed it.

There's no "Legal" ones.