Legal firms are rapidly expanding their open source practices as the legal challenges to developers and users mount.

Exact data on the expansion is not readily available, but The Recorder, a daily newspaper for the legal community in San Francisco, pointed out that several firms have doubled their open source groups over the past few years.

Intellectual property firm Townsend and Townsend and Crew told the newspaper that its open source group had expanded from two to six lawyers in just two years.

The growth reflects the increased adoption of open source, according to Philip Albert, a lawyer with the firm.

"It is really ramping up," Albert told The Recorder. "We started our practice with software companies ... and we have been expanding into medical device makers and large industrial equipment makers, and they all have open source issues."

Law firm DLA Piper has enlarged its open source practice to 12 attorneys, up from seven in 2005.

The company's open source group is headed by Marc Radcliffe, a well known technology lawyer who has worked on Sun Microsystems' Common Distribution and Development Licence and offers legal advice to the Open Source Initiative which certifies licences as open source.

Open source poses legal challenges to developers and users. Firms releasing code under an open source licence have to ensure that community contributions do not infringe on copyrights or patents.

Users, meanwhile, have to ensure that open source software can be used together with proprietary code.

Legal experts recommend that firms set policies on how to deal with open source projects, and create a list of pre-approved open source licences.