Hi,
short clarifications:
1) JavaScript is not owned by Oracle (don't confuse JavaScript with Java). Originally, JavaScript was designed by Netscape. Today, JavaScript is very popular both on the client (i.e. in all browsers) and on the server (e.g. HANA XS, node.js). There are many powerful JavaSript engines by different providers (e.g. Mozilla SpiderMonkey, Google V8, etc.), i.e. it is not bound to a single software vendor.
2) Of ocurse, ABAP can be used to develop HANA applications: all capabilities of the SAP HANA platform are fully acessible from ABAP. The main difference of the HANA Extended Application Services (HANA XS) you are refering to, is that they do not require an ABAP sytem, i.e. you can develop HANA applications directly on HANA without any additional application server. For more information how to make use of advanced HANA features from ABAP, you can have a look into many posts in this community or the HANA academy at http://www.saphana.com/community/hana-academy#Using-ABAP.
Cheers, Eric