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Business methods
Opposition to software patents is widespread in the free software community. In response, various mechanisms have been tried to defuse the perceived problem.
On the other hand, Microsoft has claimed that programs such as Linux violate 235 Microsoft patents and said that it will seek license fees.

Benefits of free software
It is quite common for patent holders to license their patents in a way that requires a per-copy fee, however, obtaining such a licence is not possible for free software projects. Free software projects cannot require mandatory royalties as these would limit distribution to only royalty payers, violating the free software definition. A patent licence that is royalty-free, or provides a one-time worldwide payment is acceptable.
Version 2 of the GNU General Public License does not allow software to be distributed if that software requires a patent licence that does not "permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you".

Problems for free software

Techniques for reducing harm
"Patent retaliation" clauses are included in several free software licences. The goal of these clauses is to discourage the licensee (the user/recipient of the software) from suing the licensor (the provider/author of the software) for patent infringement by terminating the licence upon the initiation of such a lawsuit.
The Free Software Foundation included a narrow patent retaliation clause in drafts 1 and 2 of version 3 of the GPL, however, this clause was removed in draft 3 as its enforceability and effectiveness was decided to be too dubious to be worth the added complexity.
Examples of broader clauses are those of the Apache licence and the Mozilla Public License.

Patent retaliation
In 2005, IBM, Novell, Philips, Red Hat, and Sony founded the Open Invention Network (OIN). OIN is a company that acquires patents and offers them royalty free "to any company, institution or individual that agrees not to assert its patents against the Linux operating system or certain Linux-related applications".
Novell donated the valuable Commerce One web services patents to OIN. These potentially threaten anyone who uses web services. OIN's founders intend for these patents to encourage others to join, and to discourage legal threats against Linux and Linux-related applications. Along with several other projects, Mono is listed as a covered project.

Patent pools
Movements have formed to lobby against the existence and enforceability of software patents. The earliest was the League for Programming Freedom in the USA. Probably the most successful was the anti-software-patent campaign in Europe that resulted in the rejection by the European Parliament of the Proposed directive on the patentability of computer-implemented inventions which, the free software community argues, would have made software patents enforceable in the European Union. A fledgling movement also exists in South Africa.

Microsoft's patent deals

Software patents
Software patents debate