Hello, I'm playing LEGENDS (wikipedia --> Legends_(PBM)) for quite a long time now. LEGENDS is a fanatasy strategy game which role-playing aspects. LEGENDS is based on the following fundamentals: + turn-based + multi-player-oriented + mod-enabled + simulations-realizing Currently the game has a revenue model that every turn is paid, which makes the games quite expensive. Now the time has come to take LEGENDS to its next (r)evolutionary step. I want to develop this new LEGENDS in a freeSource driven approach. Ideally the game will be developed & supported by a non-profit organisation which license the game towards commercial Play-by-eMail enterprise. Is that a valid approach? Do you have others ideas on that topic? All the best, Guido Worlds of Legends arax.wol at gmx.org

Unless you own a license to create a derivative work of or are the IP owner of the game LEGENDS, I'm going to go ahead and say that this idea, as stated in your post, is very, very bad. If you use the name LEGENDS to connote your own game product (which is based on the PBM), you have trademark infringement. If you use the manuals/games themselves, you have copyright infringement. If there's a patent in the PBM system used by LEGENDS, you may be committing patent infringement.

Altogether, as stated, fairly dangerous.