inactive sessions

Hi,

I am working in an Oracle 9i/Weblogic/J2EE platform. And when i look for session info in v$session view, i see that there are many sessions that have a status "Inactive". I already figured it out what it means- the session is ACTIVE when it is doing an SQL query at the time and the session is INACTIVE when it is not doing an SQL query at that particular moment.

But i have questions:
1) If a client logs in to my webapplication and does a SQL query- then the sessions status is ACTIVE. After that, when the client just leaves (logs out or just closes the browser) then Oracle marks that connection as 'INACTIVE'- Oracle does not KILL that session.
Ok let that be, but can another client then log in to my webapplication (from different computer) and get that same INACTIVE connection and start to use it?? If not, then these "abandoned" connection are truly useless, because they still use ORACLE resources (memory).

2)Another thing is that there are many INACTIVE sessions in v$session that have a name "plsqldev.exe" in PROGRAM column. That is a database client that i use to connect directly to my DB. But basicly i have only one PL/SQL program with one SQL query window open (this session is marked ACTIVE in v$session). So are these other 10 INACTIVE "plsqldev.exe" sessions meant for new plsql clients that may start to use the database or can only that particular user for whom the session was created at first place use that session?

And finally- sessions that are INACTIVE and have "plsqldev.exe" as a PROGRAM in v$session - is there any chance that a client logs in to webapplication and then gets that INACTIVE session?
If not, then these 10 INACTIVE plsqldev sessions (allthough the user has maybe shut down the program) are wasteless for webapplication users and they just starve the database.

Waiting for a professional answer,
Thanks!