Taxes on software/license purchases

I work as a procurement officer in BPCL. 

I want to understand what taxes are applicable on software and software license purchase.

Here is what I know till now.--

1) If the software/license is a packaged one (for general use), then only sales tax is applicable.

2) If the software is made for specific purpose for the company (say BPCL) then it attracts sales tax as well as service tax, because of the man hours invested in the making of the software for that specific purpose.

Please tell me what about excise duty on softwares. Is it applicable. Or is it service tax in place of ED? Please explain.