In 2003 Kasper Skårhøj and Andreas Otto have created a new project on SourceForge.net (SF.net) called TYPO3 Extension Development Platform (TYPO3xdev).
The purpose of TYPO3xdev is to provide a platform for extension developers where they can develop extensions together with other interested developers, rather than working as a one-man-show. One of the key advantages of TYPO3xdev is the fact that the developers do not have to care about the technical infrastructure. The development platform TYPO3xdev enables extension developers to focus on developing instead of wasting time organizing the infrastructure.
TYPO3xdev is a TYPO3 related project on SF.net which enables TYPO3 extension developers to work together using a common infrastructure. Having a common infrastructure makes it easier for developers to focus on what they are best at – developing TYPO3 extensions.
But TYPO3xdev is not just a project on SF.net it is also an example of collaborative development.
Due to the fact that TYPO3xdev is using the SF.net infrastructure the project needs at least one person who is the administrator for this project on SF.net. Only the administrator is allowed to add new developers to the project and assign write privileges to the Subversion (SVN) repository.
Each TYPO3 extension that is developed on TYPO3xdev has at least one author or maintainer and sometimes several developers assigned to the extension.

Everyone who is interested in developing TYPO3 extensions together with other extension developers can take part. The few rules to follow are outlined below.
To take part in TYPO3xdev any interested developer must have a SF.net account. The SF.net account is necessary for getting write access to the SVN repository of TYPO3xdev.
Interested developers are divided into two groups.
An extension author or extension maintainer can contact the TYPO3xdev administrator directly. The TYPO3xdev administrator needs to know the SF.net username and the TYPO3 extension key to add a new developer to the TYPO3xdev project and grant write privileges for the SVN repository to the new developer.
An extension developer willing to help with the development of at least one TYPO3 extension needs to contact the extension author or the extension maintainer. The extension author or extension maintainer will then tell the TYPO3xdev administrator the SF.net username and the TYPO3 extension key. The TYPO3xdev administrator will then grant write privileges for the SVN repository to the new developer.
All developers who are part of the TYPO3xdev project are automatically subscribed with their SF.net email addresses to the TYPO3xdev announcement mailing list.
During the last years more and more TYPO3 extension developers are using the infrastructure TYPO3xdev offers. Currently 132 TYPO3 extensions are developed by 101 developers on TYPO3xdev.
By the end of June 2006 the TYPO3xdev CVS repository was successfully migrated to SVN. Alongside with the migration of the TYPO3xdev CVS repository the CVS repository for TYPO3core was migrated to SVN as well. Both migrations happened without problems.
Since November 2006 we create nightly T3X files of all TYPO3 extensions developed using the TYPO3xdev platform. This makes it easier to install and test TYPO3 extensions before they can be uploaded to the TER.