For the moment I run Adobe Digital Editions under Wine to download ebooks burdened with ditigal restriction management. I only use it to open .acsm files supplied by ebook-shops, which contain authentication information required to download the actual DRM'ed ebook files, which I then transfer to my reader-device with calibre. My question is, if there exist open source alternatives to Adobe Digital Editions. They don't need much functionality. I just want to put the .acsm-file in and get the .epub out (no, I don't want to remove the drm, that'd be illegal afaik).
.acsm can only be used with Adobe Digital Editions and stands for Adobe Content Server Manager.
For more information about Adobe Digital Editions please see http://www.adobe.com/products/digitaleditions/faq/
Side note (may not be generally applicable to Digital Editions users): Stated in the agreement (may be of concern in making a program to access .acsm ) for Adobe Content Server section 11.1 you agree not to:
Interpret this as you will, I will not give you legal advice.