Microsoft plans to pay software maker Novell up to $100 million in additional subscription fees due to strong demand for Novell’s open-source Linux software that partners with Microsoft’s proprietary Windows software.

The payment to be made by November 1, announced by the companies on Tuesday, is in addition to a $240 million payment to Novell from Microsoft in 2006 as part of a broad set of business and technological agreements to make their products work together for corporate customers using both Linux and Windows servers.

Microsoft buys certificates from Novell and then sells subscriptions to Windows clients who want support in making their computer systems work well alongside Linux machines.