These Licenses are Perpetual License. That means, you do not have to worry about monthly or yearly subscriptions. Once you pay for a license, it is all yours and it will be valid forever. Your license will never expire.
Single Developer License (Perpetual)
Cost for each additional Developer License
This license type allows using this control by a single developer. The licensed developer can develop an unlimited number of COMMERCIAL web applications and distribute the web applications without paying any royalty.