Other than the free skills for non-member, there is also a skill for members only. Members have access to all 25 skills, other items, quests and some restrictions. You may also get more RS gold by being a member (though it is not recommended).
Members only Skills, more option for gaining more RS gold
Agility – players may able to use shortcuts. It also increases the recharge of energy. Not only that, it also increases/enhances some other skills like fishing, which you can catch multiple fishes at once. More fishes = more RS gold.
Herblore – allows players to create potions that can boost or restore skills. You may also sell those potions to other players in exchange of RS gold.
Thieving – allows players to dirty their hands and steal from market stalls and other NPC. They can also lock pick doors and treasure chests.
Fletching – players able to craft projectiles like arrows, bolts and darts, and also bows and crossbows.
Slayer – enable players to kill monsters using tactics. Some slayer monsters have a potential to give rewarding drops that only unique to them. If you’re lucky you may be able to sell it on higher price for RS gold.
Farming – players can grow plants such as fruits and vegetables, herbs and trees in certain places with patches. This skill is useful for gathering ingredients for other skills such as herblore.
Construction – players may wish to build house and furniture such chair and tables. Some houses are cost a lot so you better save up enough RS gold if you want to construct your very own dream house.
Hunter – players can track animals and use various traps for their hides.
Summoning – allows players to summon their very own familiars and pets. They can use either familiars or pets in combat and non-combat. There are some familiars who can hold additional items, meaning you can gather more items to stack on inventory and sell them for RS gold.