2012.1 AutoESL and before can be installed independently from ISE tool suite. It does also have an independent license and can perform all operations other than RTL Synthesis, which requires a RTL synthesis tool such as XST or Synplify, and implementation, which requires an ISE tool such as NGDBUILD, MAP, PAR, and Bitgen.
Downloads of AutoESL will no longer be offered and Vivado HLS should be installed instead.
For Vivado HLS, the tool will be installed with the Vivado tool suite's System or DSP edition.
AutoESL and Vivado HLS require separate license authorization. The license can be appended to the existing Xilinx license file. For licensing issues, refer to the general Xilinx licensing debug steps.(Xilinx Answer 32301).
For Vivado HLS licensing support, refer to (Xilinx Answer 51081)