I was trying to use trial version 10.4 - DOA, but getting below error:

class ERemotable Exception with message 'Direct Oracle Access trial version only runs from within the IDE'.

I thought fully free version of DOA is available for use/test for 30 days, but it seems it is not, so is that mean i need to buy the DOA license to continue further?

There is no 30 day limitation. The only limitation is that you can only run your application from within the RAD Studio IDE. This should allow you to evaluate it.

I have installed DOA as a component package, also have few custom bpls using it in their requires clause which are communicating with other dlls\bpls on running the main project. I am running the project from IDE only. Issue still persists. Any pointers for me.

Can you reboot the PC and try again? It can occasionally happen that the IDE detection fails.

It didn't worked for me. Don't know why.

It still does not work? If so, please send an e-mail to support@allroundautomations.com and we will arrange something.

Thanks for the support. Have mailed as suggested.