Dear Marcus Röckrath,
Welcome to IMSLP/Petrucci Music Library! As a composer or other copyright proprietor, please take time to carefully review the Creative Commons Licenses and the IMSLP Performance Restricted Liecense. Generally speaking, the best version to employ for new works is the Creative Commons Attribution Non-commercial No Derivatives 3.0. This allows for free downloading of the items you post, yet prohibits anyone who downloads the files from IMSLP from selling the files (on Ebay, for example), or from giving public performances on an explicitly commercial basis, making recordings of the work without written permission in advance from you, the composer and copyright owner. However, if you are affiliated with a performing rights society such as SOCAN (Canada), ASCAP, BMI or SESAC (USA), SACD, SACEM or SEAM (France), GEMA (Germany), PRS (UK), SGAE (Spain), SIAE (Italy), Artisjus (Hungary), ZAIKS (Poland), IPRO (India), JASRAC (Japan), or any of the myriad of similar agencies present in this Wikipedia listing, please note that at least some of these agencies refuse to honor the Creative Commons licenses. You should therefore seriously consider using the IMSLP Performance Restricted License for any works posted here if you are affiliated with a performance rights society.
For those uploading the first time, please remember choose the menu option "New Composition" when uploading your original works, and "Typeset" when uploading arrangements of public domain works. In the "Publisher" field, please use your own full legal name, since making your scores and sound files available for download on this site constitutes "publication" under the laws of most countries. Please do not list your works as "public domain" as it is not legally possible for your works to be fully public domain under the 'moral rights' provisions of many copyright statutes around the world. Composers and other copyright owners should be aware that Creative Commons Attribution 3.0 is very similar to public domain as it allows for the unrestricted copying, performance (live and broadcast) and recording of the work (including explicitly commercial use) at no charge, with no compensation or royalties payable to the composer or copyright owner for such commercial exploitation.