Hacktoberfest is a celebration of open-source contributions during Spooky Season, inviting participants to contribute to various repositories across the globe. The event runs from September 26 to October 31 and offers incentives such as a tree planting or a t-shirt for completing four pull requests within the designated period. Sentry's open source SDKs are participating in Hacktoberfest, welcoming new contributors and providing resources like developer documentation and live streams to aid participation. If participants find an SDK without the Hacktoberfest label, they can reach out to the DevRel team for assistance, ensuring their contributions count towards the event.