Surely, yes, if you are going to work with galacasino.org , you will may be need any sim card for the other activities to be done with it.
You can use it with a Nextel phone since Boost uses the Nextel network. I am not quit sure if you can use a Sprint phone but Sprint and Nextel are together. Did you try putting your SIM card in your Sprint phone (if it has a SIM slot)?
If your Sprint phone is a GSM/CDMA phone, your Boost Mobile SIM card will fit in the slot on the Sprint phone, however, because Boost Mobile is iDEN ONLY at this time (SIM CARD), and only uses the NEXTEL iDEN Network, and has no GSM roaming agreements currently (they are prepaid and no need for GSM roaming agreements with iDEN coverage available everywhere), unfortunately the SIM card from Boost will do no good in a CDMA/GSM only phone which is what Sprint sells.
No sprint phones do not have a sim card slot