This open source repository contains the standard QL libraries and queries that power LGTM, and the other products that Semmle makes available to its customers worldwide.
There is extensive documentation on getting started with writing QL. You can use the interactive query console on LGTM.com or the QL for Eclipse plugin to try out your queries on any open-source project that's currently being analyzed.
We welcome contributions to our standard library and standard checks. Do you have an idea for a new check, or how to improve an existing query? Then please go ahead and open a pull request! Before you do, though, please take the time to read our contributing guidelines and QL style guide.
The LGTM queries are licensed under Apache License 2.0 by Semmle.