Table 6 lists the hardware and software requirements to install and use Cisco IOS SSL VPN.
Table 5. System Requirements
Cisco SR500, 870, 880, 890, 1800, 1900, 2800, 2900, 3800, 3900, 7200 Series and Cisco 7301 Routers
Cisco IOS Software Release
Cisco IOS 12.4(9)T or later recommended
Cisco IOS Software Feature Set
Advanced Security or higher
Note: SSL VPN is supported in IOS Software. For hardware acceleration of IOS SSL VPN, a VPN AIM is required. This is supported on the Cisco 1841, 2800, and 3800 Series Integrated Services Routers
According to the licenses, as far as I know, you don't have to order SSL VPN Licenses for cisco routers anymore. Cisco changed recently the licensing schema for Anyconnect. Now you need to change AnyConnect PLUS or Apex licenses for the proper amount of users, who will use AnyConnect services. Those licenses are not tied to the hardware platform anymore.
Please, see the actual ordering guide for AnyConnect licenses: