TeamCity Editions
TeamCity comes in two editions:
Professional edition: does not require any server license key and has a limitation of maximum 20 Build Configuration configured.
Enterprise edition: edition with unlimited number of build configurations.
The editions are equal in all the features besides the maximum build configuration number allowed. The same TeamCity distribution and installation is used for both editions. You can switch to Enterprise edition by entering a license key on the Licenses page in the Administration area. All the data is preserved when edition is switched.
When an Enterprise license key is removed from the server, temporary license expires or TeamCity server is upgraded to a version released out of maintenance window of the available Enterprise license, TeamCity automatically switches to the Professional mode. See more at Licensing Policy.
Each TeamCity edition comes bundled with 3 agents. More Build Agents can be added with separate licenses.
For details on available enterprise license types, and other dealing with licenses questions please refer to Licensing Policy.
Ways to switch your server into Enterprise mode:
buy Enterprise Server license;
request 60 days evaluation license;
use TeamCity TeamCity EAP (not stable, but comes bundled with 60 day nonrestrictive license);
use TeamCity for open-source projects only. See details at Licensing Policy.