Hi Hakim,
you are raising very interesting questions about SAP HANA as development platform.
I will try a short answer here, and maybe I will create an separate general blog post about the topic, as it is very dear to me.
For the sake of clarity, let me first briefly define the term "Native HANA Application": it refers to applications making use of the SAP HANA real-time data platform, i.e. using capabilities going far beyond the capabilities of a standard, relational database (such as e.g. advanced analytics, data mining, text analysis, geo-spatial ,etc.).
These capabilities of the HANA platform are consumable via open interfaces from different programming languages and environments (with different levels of comfort). While HANA XS offers a minimal application server directly built-in into HANA which is available with every HANA installation (including SAP HANA Cloud Platform), also the Application Server ABAP has been optimized in Release 7.4 to enable ABAP developers to fully leverage and benefit from HANA.
But also other environments such as Java, .NET, and others can also make full use of HANA as platform. This is mostly done using SQL/MDX (and HTTP) based interfaces to the platform (most capabilities of the real-time data platform ultimately offer a SQL based access, using SQL as a kind of "lingua franca"). As an example, we have recently also released a HANA database driver for node.js (see https://github.com/SAP/node-hdb) based on the open SAP HANA SQL Command Network Protocol.
Best regards, Eric