The long-running legal battle between The SCO Group and IBM over source code ownership is set to become more interesting. IBM has requested that Hewlett-Packard, Microsoft, Sun and BayStar Capital turn over documents relating to their communications with SCO.

IBM filed the orders for documents and depositions on Tuesday. The orders seek communications between the companies and SCO, documents concerning efforts to maintain the secrecy of the Unix source code and information related to royalties paid for Unix.

The dispute between IBM and SCO dates back to 2003, when SCO charged IBM with offering open source software based on source code SCO claimed to own.

IBM's filings this week, however, could reveal interesting information relating to other SCO relationships, particularly with Microsoft. Just after SCO filed its lawsuit against IBM, Microsoft signed a Unix licensing agreement with SCO.

BayStar, a venture capital firm that invested in SCO, said Microsoft had referred it to SCO.

HP, Microsoft, Sun and BayStar have all been asked to hand over the documents by 7 March. The companies have each been given mid-March dates to appear for depositions as well.