Samsung thinks that SGS original is dead now. But millions of Samsung Galaxy S users are still there. They were disappointed after the release of ICS - for not getting the fun, now it is Android 4.1 or Jelly Bean.
Samsung will not release Jelly Been for SGS but there are other ways too. You can do it by custom ROM. There are custom ROMs mainly made by XDA members and can be downloaded to SGS.
Here are some guides for you about how t0 do it.
Update Samsung Galaxy S with Android 4.1 Jelly Bean
[ALPHA][ROM][4.1.1] CyanogenMod 10 for Samsung Galaxy S
Update Samsung Galaxy S I9000 to Unofficial CyanogenMod (CM) 10 – Android 4.1 Jelly Bean ROM
Did they actually give a real reason for this or do they just want their customers to jump through hoops to get what they want? I am not sure I would want to deal with something that is not fully backed by the company.