Yes, by creating a "Larger Work" under the terms of Section 3.3. In particular, three requirements must be met: The software must not be “Incompatible With Secondary Licenses.” Software can become “Incompatible With Secondary Licenses” in one of two ways: the original author marks it as such by adding the file header in Exhibit B, or the original author published the software under MPL 1.1 and did not dual- or tri-license the code with the (L)GPL. The Larger Work must be "a combination of Covered Software with a work governed by one or more Secondary Licenses." So you can't just say "I really prefer (L)GPL" - you must have a need to combine with another, existing GPL work. (This is different from a traditional dual-license, which does not require you to combine, and instead allows you to simply say "I've decided to be GPL-only.") You must "additionally distribute" under (L)GPL. In other words, you must make the MPL-licensed source code available to your recipients under both MPL and (L)GPL. Someone downstream from your recipients can then take under (L)GPL-only or MPL-only. This is different from a traditional dual-license, which never requires publication under both licenses, and so always gives you the option of releasing incompatibly-licensed code. No GPL-compatible license can perfectly preserve the original author's ability to reuse downstream derivatives, but the last two restrictions serve to increase the probability that such reuse can occur in the broadest possible set of circumstances. We have written a document explaining how to do this in practical terms, i.e. what to do about license headers and so on.